In article , Jim-P
wrote:

This makes me wonder what ISO I should set, if I don't leave it on
auto.

generally, lower iso is better and auto-iso is best left on, except for
specific situations where you want a particular iso.

however, you will want to set a maximum upper bound for auto-iso so it
doesn't raise it higher than what you consider acceptable quality.

if your camera does not have such a limit (not all do) then auto-iso
can potentially result in very noisy photos, but the alternative is no
photo or very blurry photos due to camera shake (very slow shutter
speed).

Does ISO 200 on a digital camera broadly match the grain/noise of ISO 200
Fujicolor or Kodacolor that I used to use years ago?

no. digital noise is for all intents, not noticeable until you get to
around 1600-3200 (assuming an slr class camera). for cameras with
smaller sensors, noise becomes a problem earlier.

film grain at iso 400 was acceptable, tolerable at 1600 and beyond
that, too grainy to be used other than unusual scenarios.

in other words, digital will produce vastly better quality at the same
iso.

Or do the ISO settings for a digital camera give quite different results to
the ISO values of film?

quite different in that digital is better in every way.